The lateral geniculate nucleus (LGN) of the cat was studied in terms of latency following electrical activation of the cortex and retinal afferents. These studies showed that the rarely encountered sluggishly responding classes relayed to the cortex as well as the brisk transient or sustained classes. The characteristics of LGN neurones compared to retinal afferents reinforce the idea that they are relay cells. Some brisk transient class cells from the contralateral eye have receptive fields which project well into the ipsilateral hemifield. Since these also relay to the cortex, presumably, each visual cortex is receiving information on the entire visual field. BIBLIOGRAPHIC REFERENCE: Cleland, B.G., Levick, W.R., Morystyn, R. and Wagner, H.G.: Lateral geniculate relay of slowly conducting retinal afferents to cat visual cortex. J. Physiol. 255: 299-320, 1976.